Previous studies have produced an antibody specific to prostatic acid phosphatase band 2a. This proposal includes an effort to produce monoclonal antibody to acid phosphatase band 4. The antibodies will be used for electron microscopic-immunocytochemical studies of these enzymes in prostatic as well as non-prostatic cells in order to learn the normal secretory mechanism of the prostatic epithelial cells, and look for alterations in prostatic cancer cells. Specific antibody was used to demonstrate the location of isoenzyme 2 in hyperplastic and prostatic adenocarcinoma. In hyperplastic prostate isoenzyme 2 was observed in the cisternae of Golgi apparatus and secretory granules of the columnar epithelia cells, and rarely in RER. Some isoenzyme 2 was seen in the plasma membrane and discharged into the glandular lumen. In the prostatic adenocarcinoma isoenzymne 2 was found in both columnar epithelial cells and in the basal cells. Isoenzyme 2 was seen in the cisternae of rough ER, Golgi appartus and secretory granules. Some isoenzyme 2 was seen in the interstitial spaces and occasionally in the lumen of the capillary. These findings suggest that in the hyperplastic state, isoenzyme 2 is synthesized in the RER and transported to the Golgi apparatus, and tranferred to the secretory granules for exocytosis into thelumen as expected for normal prostate. In prostatic adenocarcinoma additional isoenzyme 2 was secreted also into the basal lamina, from where it is transported to the vascular system. (5)